Patent Document 1: Japanese Published Patent Application No. S59-121216
Patent Document 2: Japanese Published Patent Application No. H09-21413
A commonly used control cable 100 consists of an outer casing 101 having flexibility and an inner cable 102 housed slidably in the outer casing 101 as shown in FIG. 11 for example. The inner cable 102 often consists of a twisted wire made by twisting metal element wires. However, in the case of light load, it is sometimes consists of a metal single wire. In the inner cable 102, cable ends (nipple) 103, 103 made of metal for engaging an operating member and an operated member are firmly fixed to the both ends by casting or clamping.
The outer casing 101 includes an armor layer 104 consisting of a spiral tube made by winding spirally a steel wire of rectangular cross section and a covering layer 105 made of synthetic resin covered on the surface of the armor layer 104. There is also a case that a liner made from synthetic resin tube is provided in the inner face of the armor layer 104. Further, an armor layer may be composed around the liner with a shield layer in which a plurality of wire members made of metal or hard synthetic resin is arranged in a loose spiral shape. In the both ends of the outer casing 101, casing caps 106, 106 made of metal or synthetic resin are covered and firmly fixed by clamping etc.
In such control cable 100, the outer casing 101 is arranged along a curved cabling path, and the casing caps 106, 106 of the both ends are engaged with a bracket 107 etc. Further, the cable ends 103, 103 of the both ends of the cable 102 are engaged with an operating member 108 and an operated member 109 etc. and are attached. And, the operating member 109 is operated by push-pull action, which transmits the operating force to the operated member 109 to perform remote control.
Since the commonly used control cable 100 described above is equipped with the armor layer 104 in the outer casing 101, even if a large tensile force is applied to the inner cable 102, it can support the reactive force. Hence, it can transmit a large operating force.
On the other hand, in a light load cable, a simple control cable is used. The cable consists of an outer casing made from synthetic resin pipe and an inner cable housed slidably in the outer casing. In this outer casing also, casing caps, are fixed firmly to the both ends, and the cables are laid along a cabling path by being engaged with brackets etc. respectively. However, since the pipe made of synthetic resin is very high in thermal expansion coefficient compared with metal, if it is laid in an engine room etc. there is a problem that outer casing extends/contracts according to ambient temperature.
For example, when the ambient temperature becomes high, the length of the outer casing becomes long relatively to the inner cable, the sum (A+B) of the length A, B of the portion protruding from the outer casing of the inner cable becomes shorter than that in the time of attachment. Hence, despite that the inner cable is not really operated, it comes into a status being pull-operated, causing the malfunction of the operated member.
In order to solve such a problem, Patent Document 1 offers an outer casing 117 which is, shown in FIG. 12, reinforced by embedding two reinforcing fibers 116, 116 in the both sides of a central hole 115 to pass an inner cable of a pipe 114 made of thermoplastic resin. Additionally, in Patent Document 1, it is described that the reinforcing fibers are preferable to be 2-10 in number (claim 2), and that as the reinforcing fiber, a carbon fiber, a glass fiber, a Keplar fiber (that in which a plurality of fibers are twisted) are preferable (claim 3). Further, it is described that if steel wires are used, the flexibility becomes impaired because the rigidity becomes too large (comparable example 3, the upper left column 12-15 of page 3 of Patent Document 1).
On the other hand, in Patent Document 2, a push-pull control cable which passes two inner cables in one outer casing is disclosed.